Corrosion resistant article and methods of making

Patent metadata

Field	Value
Publication number	US-2016207110-A1
Application number	US-201514600083-A
Country	US
Kind code	A1
Filing date	Jan 20, 2015
Priority date	Jan 20, 2015
Publication date	Jul 21, 2016
Grant date	—

Abstract

An article and method of forming the article are disclosed. The article has a surface comprising a duplex nanostructured ferritic alloy. The surface includes a plurality of nanofeatures that include complex oxides of yttrium and titanium disposed in an iron-bearing alloy matrix. The iron-bearing alloy matrix includes both a ferrite phase and an austenite phase. Further, a concentration of a chi phase or a sigma phase in the duplex nanostructured ferritic alloy at the surface is less than about 5 volume percent. The method generally includes the steps of milling, thermo-mechanically consolidating, annealing, and then cooling at a rate that hinders the formation of chi and sigma phases in the duplex nanostructured ferritic alloy at the surface.

First claim

1 . An article, comprising:
a surface comprising a duplex nanostructured ferritic alloy, the alloy comprising a plurality of nanofeatures disposed in an iron-bearing alloy matrix, the plurality of nanofeatures comprising complex oxide particles, wherein the complex oxide particles comprise yttrium and titanium; the iron-bearing alloy matrix comprising both a ferrite phase and an austenite phase, wherein
a concentration of a chi phase or a sigma phase in the duplex nanostructured ferritic alloy is less than about 5 volume percent.

2 . The article of claim 1 , wherein the ferrite phase in the iron-bearing alloy matrix is in a range from about 10 volume percent to about 50 volume percent of the matrix.

3 . The article of claim 1 , wherein the austenite phase in the iron-bearing alloy matrix is in a range from about 50 volume percent to about 90 volume percent of the matrix.

4 . The article of claim 1 , wherein a total concentration of the chi phase and the sigma phase is less than about 5 volume percent.

5 . The article of claim 1 , wherein a concentration of titanium in the duplex nanostructured ferritic alloy surface is in a range from about 0.15 wt % to about 2 wt %.

6 . The article of claim 1 , wherein the matrix phase comprises chromium in an amount from about 20 weight percent to about 27 weight percent.

7 . The article of claim 1 , wherein the matrix phase comprises nickel in an amount from about 5 weight percent to about 8 weight percent.

8 . The article of claim 1 , wherein the matrix phase comprises molybdenum in an amount from about 1 weight percent to about 5 weight percent.

9 . The article of claim 1 , wherein the matrix phase comprises nitrogen in an amount from about 0.2 weight percent to about 0.3 weight percent.

10 . The article of claim 1 , wherein the matrix phase comprises tungsten in an amount less than about 1 weight percent.

11 . The article of claim 1 , wherein the surface is substantially free of chi phase.

12 . The article of claim 1 , wherein the surface is substantially free of sigma phase.

13 . The article of claim 1 , wherein the nanofeatures have an average size in a range of from about 1 nanometer to about 50 nanometers.

14 . The article of claim 1 , wherein the nanofeatures have a number density in a range from about 10 21 to 10 24 per cubic meter of the duplex nano structured ferritic alloy.

15 . The article of claim 1 , wherein a grain size of the matrix is in a range from about 0.2 micron to about 1 micron.

16 . A method, comprising:
milling an iron-bearing alloy powder in the presence of yttrium oxide until the oxide is substantially dissolved into the alloy; thermo-mechanically consolidating the powder to form a consolidated component; annealing the consolidated component to form an annealed component; cooling the annealed component to form a processed component,
wherein the processed component comprises a surface comprising a duplex nanostructured ferritic alloy, the duplex nanostructured ferritic alloy comprising:
a plurality of nanofeatures disposed in an iron-bearing alloy matrix, the plurality of nanofeatures comprising complex oxide particles, wherein the complex oxide particles comprise yttrium and titanium; and
the matrix comprises both a ferrite phase and an austenite phase,

wherein a concentration of a chi phase or a sigma phase in the duplex nanostructured ferritic alloy at the surface is less than about 5 volume percent; and
wherein the annealing step is performed at a temperature above the solvus temperature of the chi phase and the sigma phase.

17 . The method of claim 16 , wherein the step of thermomechanically consolidating comprises hot isostatic pressing, extruding, hot forging, cold forging, compacting, or a combination of any of these.

18 . The method of claim 16 , wherein a concentration of chromium is in a range from about 20 weight percent to about 27 weight percent, a concentration of nickel is in a range from about 5 weight percent to about 8 weight percent, a concentration of molybdenum is in a range from about 1 weight percent to 5 weight percent, a concentration of nitrogen is in a range from about 0.2 weight percent to 0.3 weight percent, a concentration of tungsten is less than 1 weight percent.

19 . The method of claim 16 , wherein the surface is substantially free of chi phase.

20 . The method of claim 16 , wherein the surface is substantially free of sigma phase.

Assignees

• Gen Electric

Inventors

• Huang Shenyan
• Rebak Raul Basilio
• Didomizio Richard
• Pietrangeli Emanuele

Classifications

• B22F3/16 Primary

  in successive or repeated steps · CPC title

• B22F3/17

  by forging · CPC title

• B22F2003/175

  by hot forging, below sintering temperature · CPC title

• B22F3/14

  simultaneously · CPC title

• B22F3/20

  by extruding · CPC title